It is highly desirable and beneficial to provide flexible containers of the type used for the storage and dispensing of diverse products such as motor oil, transmission fluid, and various other types of motor vehicle additives that have to be poured from the container, with an improved leak proof closure seal that includes a pressure activated self opening feature.
Such container types are comprised of a tubular body portion with a sealed bottom end. An opposite top end is comprised of a funnel shaped neck forming a pour spout that includes means for securing a closure cap. The pour spout ends with an exterior rim that provides a surface area for bonding a seal over the pour spout opening.
This one piece container has gained wide acceptance since introduced and was designed to replace the problematic metal and paperboard can type container being used at the time. Not only did the can type container suffer from a high leakage rate it would also most likely burst when dropped. Additionally, in order to open the container and dispense the contents, a user was required to provide either a can opener and fill funnel or a reusable metal pour spout attachment that was pushed into the can top, piercing the metal, and secured by a press fit. This was an inconvenience and as can be seen the much stronger and durable plastic bottle was a great improvement that has made the can type container obsolete.
When such flexible bottle type container replacements first came into popular use, there were problems associated with the design of the closure caps that caused seepage and leaking of the contents in many containers beyond acceptable limits. To overcome this flaw many manufacturers added a durable foil seal that was bonded over the pour spout opening by induction sealing and was very effective in preventing any leakage prior to the consumer removing the closure cap and seal. Although performing well in this function, these seals proved to be extremely difficult to be removed by hand, requiring the consumer to provide a sharp tool just to open the product.
To correct this fault and to promote product ease of use and consumer convenience manufacturers made advances in closure cap technology and sealing materials for preventing leakage. The induction bonded foil seal was phased out by many manufacturers and replaced with a resilient gasket that is bonded to the underside of the container closure cap and is the primary method currently used by most manufacturers to prevent leakage of the contents.
However, despite the advances made in closure caps to prevent leakage, they have fallen far short of solving the problem. Incorrect torqueing of the screw on closure cap, dropping of the container, jarring through shipping or loading, or poor fit of the gasket, can all cause container leakage prior to the removal of the closure cap. Even with the addition of a locking tear strip at the lower outer perimeter of the closure cap this type of container can still leak and contains no backup provision to prevent it.
In addition to problems with leakage, a second and more serious disadvantage with the flexible plastic container as currently provided, is the extreme difficulty a user experiences when trying to pour the liquid from the container into a narrow fill opening without the contents spilling everywhere.
In order to accomplish this task, a consumer has to judge where to position the container and then begin to slowly invert the container while trying to keep the pour spout exactly in the right place for the liquid to pour into the fill opening. At this point the consumer has to try to bring the pour spout closer to the fill opening so it can be inserted as the container contents continue to pour out. This has to be accomplished as the liquid stream pulses from air being drawn back into the container to equalize the container pressure. An extremely difficult task even in the best of conditions.
When attempting this procedure it becomes obvious that the likely outcome is the container contents end up being spilled into the engine compartment and then drip on to the ground and pollute the environment. A more serious consideration is the possibility of the contents flowing onto hot engine components creating noxious fumes and possible fire.
Although a motorist can avoid this by using a fill funnel, this also has its drawbacks, the funnel becomes covered by the container contents and has to be cleaned after each use or too often a funnel isn't available when needed. Garages with an attendant to provide this service have largely been replaced by self service facilities where there is usually no funnel available. Recognizing this need, some self serve gas stations provide a disposable paper funnel, but then a further problem is, these paper funnels become hazardous waste when soaked with petroleum products, are a waste of natural resources, and are of a considerable cost to the consumer in the form of higher prices.
These disadvantages are well known and could be effectively eliminated by the bonding of a leak proof frangible seal over the pour spout opening that is only of sufficient strength to remain intact when subjected to the pressure created by the weight of the liquid contents when the filled uncapped container is held in an inverted position. At the same time the seal would also have to be sufficiently weak enough to fail and burst open from the additional pressure that can be brought to bear against the seal by a consumer squeezing or striking the filled uncapped container when held in the inverted position. A container seal that incorporated this self opening feature would allow a user to invert the filled uncapped container and then insert the pour spout into the fill opening without spilling the contents. Then by pressurizing the container by compression, the seal would break open and dispense the contents only into the fill opening thereby eliminating the need of an opening device or fill funnel.
There have been numerous patents granted for container closure seals that include this feature. The prior art patents described herein offer similar and differing designs, materials, and fabrication methods in attempting to provide a pressure activated self opening closure seal that functions in this manner.
U.S. Pat. No. 4,696,328 to Rhodes Jr. describes an embodiment of a single layered airtight rupturable plastic container seal that is bonded to the pour spout rim of a flexible oil bottle that stretches, bursts open, and tears apart in an undefined configuration thereby dispensing the contents when the inverted container is squeezed by a consumer.
U.S. Pat. No. 4,789,082 to Sampson describes an embodiment of a single layered seal for an oil bottle consisting of fabric, metal foil, or plastic wherein a first portion of the seal is bonded to the pour spout rim of a flexible container with a releasable adhesive that allows the seal to detach from the rim and dispense the contents when the inverted container is squeezed by a consumer. A second portion of the seal is bonded to the rim with a fixed adhesive which keeps the seal attached to the pour spout after the container is squeezed to open the seal.
U.S. Pat. No. 4,938,390 to Markva describes a number of embodiments of a sealing closure for an oil bottle. A first embodiment describes a single layered seal wherein a first portion of the seal is bonded to the pour spout rim of a flexible container with a releasable adhesive that allows the seal to detach from the rim and dispense the contents when the inverted container is squeezed by a consumer. A second portion of the seal is bonded to the rim with a fixed adhesive which keeps the seal attached to the pour spout after the container is squeezed to open the seal. A second embodiment describes a single layered seal with various tear lines that is bonded to the pour spout rim of a flexible container wherein no portion of the seal releases from the rim, but tears open along the lines and dispenses the contents when the inverted container is squeezed by a user. A third embodiment describes a single layered seal, with a tear line that extends across its diameter, that is bonded to the pour spout rim of a flexible container. Portions of the seal are bonded to the rim with a releasable adhesive that allows the seal to tear open in two halves along the tear line and partially detach from the rim and dispense the contents when the inverted container is squeezed by a user. A portion of each torn half is bonded to the container rim with a fixed adhesive which keeps the detached portions attached to the pour spout. A fourth embodiment describes a seal that consists of a first layer with tear lines that is bonded to the pour spout rim of a flexible container covering over a portion of the pour spout opening wherein no portion of the layer releases from the rim. The remainder of the pour spout opening is covered over by a second layer that partially overlaps, and is bonded to, the first layer and a portion of the rim with a releasable adhesive that allows the second layer to delaminate from the first layer and a portion of the rim to dispense the contents when the inverted container is squeezed by a user. A portion of the second layer is bonded to the container rim with a fixed adhesive which keeps the delaminated layer attached to the pour spout. A fifth embodiment describes a seal that consists of a first layer with an opening and a tear line that is bonded to the pour spout rim of a flexible container wherein no portion of the layer releases from the rim. The opening in the first layer is covered over by a second layer that is bonded to the first layer with a releasable adhesive that allows the second layer to delaminate from the first layer and dispense the contents when the inverted container is squeezed by a user. A portion of the second layer is bonded to the first layer with a fixed adhesive which keeps the delaminated layer attached to the first layer.
U.S. Pat. No. 4,949,857 to Russell describes an embodiment of a single layered rupturable seal of non absorbent material that is bonded over the pour spout mouth of a flexible oil bottle. The seal contains an X shaped breaking pattern consisting of weakened lines that rupture and dispense the contents when the inverted container is squeezed by a consumer.
U.S. Pat. No. 5,353,968 to Good Jr. describes a number of embodiments for a single layered closure for a flexible container consisting of varying materials that has lines or areas of relative weakness on its surface. In a first embodiment the lines or weakened portion consists of an X shaped score that can partially penetrate the closure or be a slit, that blows out and dispenses the contents when the inverted container is squeezed by a consumer. In a second embodiment the lines or weakened portion consists of an X shaped series of perforations penetrating the closure that allow the closure to blow out and dispense the contents when the container is squeezed by a consumer. In a third embodiment the weakened portion consists of a thinned central area formed by compression, boring, or any other suitable means that blows out and dispenses the contents when the inverted container is squeezed by a consumer. If any of the above described embodiments of the closure are used on a container of engine oil, the closure may be made of a plastic that melts when any pieces of the closure break off and contaminate the product going into the engine.
U.S. Pat. No. 5,634,504 to Chandler describes a single layered closure seal consisting of metal foil with a layer of hot melt adhesive used to heat seal the closure to the container rim. The closure seal contains a repeating fracture pattern that allows the seal to burst open and tear along the lines of the fracture pattern when the container is inverted and squeezed by a consumer. The seal contains vent holes to equalize the internal container pressure with the atmospheric pressure.
The prior art patents described herein collectively employ a number of similar and differing seal design and fabrication methods in attempting to construct a container closure that bursts open when subjected to container squeezing pressure. However, each of the embodied design methods employed by the prior art and described herein, manifest similar and differing drawbacks.
A first method makes use of a single layered seal that is bonded over the container opening with a fixed adhesive. The seal bursts open in an undefined configuration when sufficient pressure is applied by squeezing the inverted container such as described in U.S. Pat. No. 4,696,328 to Rhodes Jr. However, this method gives no provision for the possibility that portions of the seal material may tear away and contaminate the contents when opened which could damage the motor by clogging the internal flow of lubrication to critical components.
A second method makes use of a single layered seal that is bonded over the container opening with a fixed adhesive. The seal bursts open in a central thinned area when sufficient pressure is applied by squeezing the inverted container such as described in an embodiment of U.S. Pat. No. 5,353,968 to Good Jr. To overcome the drawback that portions of the seal material may tear away and contaminate the contents when opened, which could damage the motor by clogging the internal flow of lubrication, the seal can be made from a material that melts in the heated oil when the motor reaches its operating temperature. However, with this method there is no provision given for the possible damage that may be caused to the motor by altering the lubricating qualities of the oil by repeatedly contaminating it with melted seal material, or that portions of the seal material may tear away when opened and damage the motor during warm up by clogging the internal flow of lubrication to critical components when a consumer inadvertently adds oil to a cold engine. There is also the inconvenience of having to wait for the motor to warm up before being able to add oil.
A third method makes use of a single layered seal that is bonded over the container opening with a releasable adhesive wherein one or more portions of the seal delaminate from the rim when sufficient pressure is applied by squeezing the inverted container. The seal material is kept from completely detaching from the container by bonding one or more portions of the seal to the pour spout with a fixed adhesive such as described in U.S. Pat. No. 4,789,082 to Sampson and embodiments of U.S. Pat. No. 4,938,390 to Markva. However, with this method there is no provision given for the possibility that using a releasable adhesive with a bond strength that is weak enough to allow the seal to delaminate from the container rim when the inverted container is squeezed, would also allow the seal to delaminate when the closure cap is rotated. The amount of pressure applied against the seal when the closure cap is torqued on or off is many times greater than the small amount of adhesive strength required to allow the seal to delaminate from the pour spout rim when the inverted container is squeezed. Rotation of the closure cap while it is compressed against the seal during installation or removal produces a shearing force that could force the releasable portion of the seal to lose its bond and rotate with the cap which would cause the seal to pleat against the fixed portion resulting in leakage and opening of the seal. Additionally a tack type releasable adhesive with low adhesion characteristics could also be vulnerable to degradation from the volatile organic compounds present in many petroleum based products that could negatively affect the seals ability to remain bonded to the container rim when a given pressure is brought to bear.
A fourth method makes use of a seal that consists of a first layer with an opening that is bonded to the container rim with a fixed adhesive. The opening is covered over by a second layer that is bonded to the first layer with a releasable adhesive that allows the second layer to delaminate from the first layer when sufficient pressure is applied by squeezing the inverted container. The second layer is kept from completely detaching from the container by bonding a portion of the second layer to the first layer with a fixed adhesive such as described in embodiments of U.S. Pat. No. 4,938,390 to Markva. Again, with this method, there is no provision given for the possibility that using a releasable adhesive with a bond strength that is weak enough to allow the second layer to delaminate from the first layer when the inverted container is squeezed, would also allow the second layer to delaminate from the first layer when the closure cap is rotated. The amount of pressure against the seal when the closure cap is torqued on or off is many times greater than the small amount of pressure required to allow the second layer to delaminate from the first layer when the inverted container is squeezed. Rotation of the closure cap while it is compressed against the seal during installation or removal produces a shearing force that could force the releasable portion of the second layer to lose its bond and rotate with the cap which would cause the second layer to pleat against the fixed portion resulting in leakage and opening of the seal. Additionally a tack type releasable adhesive with low adhesion characteristics could also be vulnerable to degradation from the volatile organic compounds present in many petroleum based products that could negatively affect the second layers ability to remain bonded to the first layer when a given pressure is brought to bear.
A fifth method makes use of a single layered non leak proof seal that is bonded over the container opening with a fixed adhesive. The seal contains a weakened fracture pattern with vent holes or an area that is weakened by perforations or creased slits and when sufficient pressure is applied by squeezing the inverted container the seal is forced to burst open and tear only in the configuration of the fracture pattern, perforations or slits as described in embodiments of U.S. Pat. No. 4,938,390 to Markva, embodiments of U.S. Pat. No. 5,353,968 to Good Jr. and U.S. Pat. No. 5,634,504 to Chandler. However, with this method there is no provision given for the problem of the seal leaking through the perforations, slits, or vent holes during shipping or handling. To prevent this, it would be necessary to include an additional seal in the form of a resilient gasket between the closure cap and the seal which would increase the cost of the container. Additionally, the vent holes, slits, or perforations would also leak from the pressure created when the container is gripped and inverted by a consumer which would allow the container contents to drip into the motor compartment making a mess or worse drip onto hot engine components creating noxious fumes and possible fire.
A sixth method makes use of a single layered seal that is bonded over the container opening with a fixed adhesive. The seal contains a weakened breaking pattern that is created by thinning the seal material. Various thinning techniques are employed by the prior art to accomplish this, including; scoring, milling, boring, compression, molding or laser cutting. When sufficient pressure is brought to bear against the seal by squeezing the inverted container, the seal is forced to burst open and tear only in the weaker thinned area of the breaking pattern configuration as described in U.S. Pat. No. 4,949,857 to Russell, and embodiments of U.S. Pat. No. 5,353,968 to Good Jr. However, using any of the various techniques described in these two prior art patents to fabricate a thinned breaking pattern that will leave the precise material thickness necessary for the seal to remain intact when the filled container is lightly gripped and inverted, and then consistently burst at a squeezing pressure that by necessity has to be very low, present considerable manufacturing and fabrication drawbacks described herein.
The burst pressure of the seal cannot be determined by the maximum amount of squeezing force that a consumer can comfortably apply to the inverted container. The higher the burst pressure of the seal, the more likely the volume of liquid gushing out of the container pour spout will exceed the inflow capacity of the fill opening which will cause the liquid to back up and overflow when the seal bursts open. Therefore it is essential that the amount of additional squeezing force necessary to burst open the seal when the container is held by a consumer in the inverted position must be kept as close to zero as possible, while still leaving the seal strong enough to remain intact when the filled uncapped container is gripped and inverted.
Additionally, the laws of fluid dynamics dictate that because the bore of the container is many times greater than the bore of the pour spout opening, the squeezing pressure applied to the container will also be many times greater than the pressure that the squeezing action brings to bear against the seal. This has the effect of multiplying the amount of squeezing pressure necessary to burst the seal and, consequently, will equally increase the internal pressure of the container and the volume of liquid gushing out of the pour spout when the seal breaks open. This further adds to the requirement that any additional thickness of material in the thinned area greater than that necessary for the seal to remain intact when the container is gripped and inverted, must be kept to the absolute minimum that is practically attainable.
When the uncapped container is inverted, the weight of the liquid contents together with the additional pressure created by a consumer gripping the container, produces lateral force that pushes against the seal. This lateral force creates tension in the seal that is opposed by the tensile strength of the seal material. For the seal to burst the lateral force must be increased to a degree sufficient to overcome the tensile strength of the seal material in the thinner area of the breaking pattern. The tensile strength of the seal material, and henceforth the amount of container pressure required to burst the seal, is determined by the type of material used and its thickness in the thinned area. When the tensile strength of the seal material being used and the required burst pressure of the seal are known, the exact minimum material thickness necessary for the seal to remain intact when the container is gripped and inverted, can be determined.
For example, because of its reliability, low cost, and adaptability to high speed fabrication and installation, the packaging industry has universally adopted induction sealing as the method of choice for installing closure seals on many types of containers including those used for pourable motor vehicle additives.
One such type of induction bonded container seal is comprised of a layer of metal foil with one side coated with a layer of hot melt adhesive. The opposite side of the foil seal can be laminated to a layer of absorptive material, such as pulp board, with a layer of heat releasable adhesive, such as micro crystalline wax. The assembled seal disk is inserted into the closure cap which is then installed over the pour spout opening. This presses the hot melt adhesive side of the seal against the container rim. The container is then passed through an induction sealer that generates a high voltage field which is conducted by the metal foil layer of the seal causing it to heat up. The hot foil layer in turn melts the hot melt adhesive layer which bonds the seal to the container rim and simultaneously melts the wax layer which is then absorbed into the pulp board thereby releasing the seal. The pulp board is then retained in the cap when it is removed from the container leaving only the foil seal bonded over the container opening.
Another type of seal that is induction bonded to the container rim in the same manner is comprised of a layer of metal foil with one side coated with a layer of hot melt adhesive. The opposite side of the foil seal can be permanently laminated to one or more layers of various materials, such as synthetic foams, papers, polymer films, plastics, etc. that perform different functions such as providing even compression against the container rim or stiffening the seal to provide resiliency for peripheral tabs that allow the seal to be retained in the closure cap without using releasable layers.
Because of its high conductivity, high strength to weight ratio, low cost, and other desirable qualities, aluminum is used almost exclusively in the industry for the foil layer Excluding the hot melt adhesive layer, which is generally thicker and stronger than the foil layer, the aluminum foil used for these seals is typically a few thousandths of an inch thick. Based on the volumetric weight of the contained liquid and the width of the pour spout opening of a typical container of the type described herein, the pressure produced and brought to bear against the seal when the container is lightly gripped and inverted can be held by an adhesive free single layered aluminum foil seal with a thin breaking pattern that measures approximately one ten thousandth of an inch thick (0.0001″) and is herein referred to as the base thickness. Even a base thickness of two ten thousandths of an inch (0.0002″) produces a bursting pressure that is far too high. Therefore, in order for the seal to consistently burst with the minimal amount of additional container pressure required, the base thickness of the seal material in the thinner area of the breaking pattern must be able to be adjusted with an accuracy that approaches one one hundredth thousandth of an inch thick (0.00001″), and if other types of seal material are used, the base thickness of the breaking pattern using those materials would also have to be able to be adjusted with similar dimensional accuracy in order for the seal to burst at the precise pressure required.
As can be seen, setting the exact burst pressure necessary for a self opening seal to function properly requires a seal design that allows the process of thinning the material to form the breaking pattern to be controlled with extreme precision. When a weakened breaking pattern has to be created by thinning an area of the seal material to approximately one ten thousandth of an inch thick, within tolerances approaching one one hundredth thousandth of an inch (0.00001″), as is the case with aluminum foil, each of the various thinning schemes used in the prior art patents such as; scoring, milling, boring, compression, molding, or laser cutting fail to provide the control necessary to meet these requirements.
For example, forming the thinned area of the breaking pattern in the seal material by scoring requires that some type of cutting tool be drawn across the surface of each individual seal. This requires that the scoring tool must be kept approximately one ten thousandth of an inch above the bed of a scoring machine as it cuts a relatively deep breaking pattern into a thin layer of delicate seal material while also keeping the depth of the score within tolerances approaching one one hundredth thousandth of an inch. It should be immediately obvious even to those unskilled in the art, that the seal material will most likely tear when this is attempted. Even if this could be accomplished at all, it would be a very time consuming process that would most likely produce quality control problems, a high defect rate and cause inconsistent burst pressures from one seal to the next.
To form the thinned area of the breaking pattern by boring or milling requires that a rotating cutter be kept approximately one ten thousandth of an inch above the bed of a machine tool as it cuts a relatively deep breaking pattern into a thin layer of delicate seal material while also trying to maintain the depth of the cut to within tolerances approaching one one hundredth thousandth of an inch. Again, it should be immediately obvious even to those unskilled in the art that the seal material will most likely tear when this is attempted. Even if this could be accomplished at all, it would also be a very time consuming process that would again, most likely produce quality control problems and a high defect rate and cause inconsistent burst pressures from one seal to the next.
Creating the thinned area of the breaking pattern by compression would require that some type of die, knife edge or V shaped anvil be pressed into various seal materials. Again, the ability to consistently control the depth of a groove that leaves the thinned area of the breaking pattern with the extremely thin and precise dimension necessary for the seal to function properly is beyond the capabilities of a die press. Drawbacks such as allowable machine tolerances or incremental tool wear alone would be sufficient to also produce defects that could cause inconsistent burst pressures from one seal to the next.
Manufacturing a self opening seal with a thinned breaking pattern using a molding process such as injection or vacuum forming requires the seal to be fabricated from heated plastic material which presents a number of significant disadvantages. Each seal must be made individually and cannot be stamped out from roll stock in a high speed fashion. Because of the elasticity and expansion coefficient of plastic materials, the ability to consistently control the depth of the thinned area of the breaking pattern to the tolerances required is beyond the capabilities of either process. Injection molding and vacuum forming also require expensive multi cavity molds that must be replaced regularly adding to the unit cost of each seal. Additionally, manufacturing the closure seal by molding is a time consuming process which would also add to the unit cost of each seal.
Creating the thinned area of the breaking pattern by laser cutting would present different but even more intractable problems. Attempting to melt the seal material to a particular depth with a laser will not produce a precisely thinned breaking pattern. An industrial laser is ideally suited to cutting completely through any type of material in a very precise manner, for instance, to create slits or perforations, but it is inefficient when attempting to use it as a scoring device or milling machine. The process of thinning the seal material by the use of a laser requires the beam to be of sufficient heat to vaporize the seal material to a precise depth. A laser beam that is hot enough to vaporize any type of seal material would not just stop at a certain depth when the laser is either pulsed or moved across the surface. Vaporizing the seal material with the use of a laser is an explosive event that would not leave the precisely thin and delicate layer of intact material necessary for the seal to function properly, if it left any material at all. This method would also be a time consuming process that would add to the unit cost of each seal.
As can be seen when U.S. Pat. No. 4,949,857 to Russell and U.S. Pat. No. 5,353,968 to Good Jr. are closely examined, each falls far short of providing a self opening seal structure that allows the thickness of the material in the thinned area of the breaking pattern to be controlled with the precision necessary for the seal to consistently burst at the precise pressure required. Additionally, the structure of each of the seal embodiments require fabrication methods do not allow the closure to be easily manufactured in a high speed manner that will produce a defect free seal at the lowest possible cost.
In addition to the aforementioned drawbacks in all of the prior art patents, a further drawback is the inability of any of the closure seal embodiments to be manufactured and bonded over a container opening by using the existing induction sealing process which is a significant disadvantage.
For instance, the closure seal of U.S. Pat. No. 4,696,328 to Rhodes Jr. is fabricated from thin rupturable plastic that will not conduct a high voltage current.
The closure seal of U.S. Pat. No. 4,789,082 to Sampson uses both a first fixed adhesive that would have to be a hot melt type and a second releasable adhesive that could migrate to the area between the fixed adhesive and the rim when the closure cap is rotated under pressure which could degrade the ability of a hot melt adhesive to provide a proper bond.
The closure seal of U.S. Pat. No. 4,938,390 to Markva uses variations of two different self opening designs. A first design consists of a one or two layered seal that uses both a first fixed adhesive that would have to be a hot melt type and a second tacky releasable adhesive that could migrate to the area between the fixed adhesive and the rim or between the fixed adhesive of a first layer and a second layer when the closure cap is rotated under pressure which could degrade the ability of a hot melt adhesive to provide a proper bond. A second design consists of a single layered seal containing what appears to be various perforated tear line configurations. The hot melt adhesive layer used to bond an induction seal to a container rim becomes viscous when melted which could cause the adhesive to reseal the perforations of the tear lines and prevent the seal from bursting. To eliminate this requires that the adhesive be zone specific applied to each individual seal only in the area contacting the rim, an inefficient and time consuming process that cannot be incorporated into the existing induction sealing process.
The closure seal of U.S. Pat. No. 4,949,857 to Russell uses a weakened breaking pattern that would be prevented from bursting by the underlying layer of hot melt adhesive, also requiring the adhesive to be zone specific applied to each individual seal only in the area contacting the rim, again an inefficient and time consuming process that cannot be incorporated into the existing induction sealing process.
The closure seal of U.S. Pat. No. 5,353,968 to Good Jr. uses two variations of two different designs for a self opening seal. A first design consists of a closure seal with a breaking pattern that is weakened by slits or perforations. A second design consists of a closure seal with a breaking pattern that is weakened by being thinned in various ways. Again, the necessary layer of hot melt adhesive prevents both designs from being able to be adapted to the induction sealing process either by resealing the slits or perforations when melted or not allowing the thinned area of the breaking pattern to burst when the container is pressurized. To over come this the hot melt adhesive would also have to be zone specific applied to each individual seal only in the area contacting the rim, again a time consuming process for fabricating large quantities of the closure seal that cannot be incorporated into the existing induction sealing process.
The closure seal of U.S. Pat. No. 5,634,504 to Chandler uses a single layered seal that contains vent holes and what appears to be either a perforated or scored fracture pattern. In either case the necessary layer of hot melt adhesive would again prevent the seal from bursting properly by possibly resealing the narrow perforations when the adhesive melts or preventing the seal from bursting at all if just scored, thereby requiring that there be no adhesive in the area of the scores or perforations. Again, the adhesive would have to be applied in a zone specific fashion only in the area where the seal contacts the rim of the container which cannot be incorporated into the existing induction sealing process.